Testosterone, Total

A total testosterone test measures almost all the testosterone in your blood, the roughly 98% bound to carrier proteins plus the small free fraction, from a single blood draw. ³ Two things decide whether the number means anything: when it was drawn, and how much of it is bound. Testosterone peaks in the early morning and falls through the day, so it should be a morning draw, ideally fasting, repeated once to confirm. Because most of it is stuck to proteins that keep it out of your tissues, a normal total can sit on top of a low free level. The total opens the workup; free testosterone and a repeat draw finish it.

How to test testosterone levels

The test is a blood draw, usually a single tube, and it is often bundled with SHBG, LH, FSH, and sometimes free testosterone on a hormone panel. Getting a usable answer depends less on the lab and more on how the sample is collected.

1. 1Draw it in the morningTestosterone peaks in the early morning and drifts down through the day, so guidelines call for a sample before about 10am. [[1]]
2. 2Fast beforehand if you canEating, especially a sugar load, can transiently lower testosterone, so an overnight fast is preferred to keep the reading clean. [[5]]
3. 3Confirm a low valueA single low result is unreliable. Repeat it on a second morning, fasting sample before treating the number as real. [[1]]
4. 4Add SHBG and free testosterone when neededIf the total is borderline, or SHBG is likely off (older age, obesity, thyroid or liver disease), a free or calculated free testosterone gives a truer read. [[1]][[3]]

The chart shows the practical problem. The same man can look normal at 8am and 'low' by mid-afternoon, so a lone afternoon value, or a single borderline morning value, settles nothing on its own.

What is a normal testosterone level in men?

The harmonized reference range for total testosterone in healthy, non-obese men aged 19 to 39 is 264 to 916 ng/dL (9.2 to 31.8 nmol/L), measured with CDC-standardized assays (standardized lab test methods). ² New to how labs set these cutoffs? See how reference ranges work. Much of the disagreement between older lab ranges came from the assays themselves, not from real differences between men. Testosterone also declines gradually with age, so an older man's average sits lower, but the guideline still reads results against the young-adult range and leans on symptoms to decide what a number means.

The guidelines do not give you an 'optimal' target. There is a reference range, and there is symptom relief if a man is treated, but no evidence-based number to aim for in an untreated man. A total of 700 is not 'better' than 500 if you feel well. The workup follows the symptoms.

Total vs free testosterone: the fraction that reaches your tissues

Only a small slice of your testosterone can reach your tissues. Roughly 98% is bound: about 44% clings tightly to SHBG (sex hormone binding globulin) and about 54% is loosely held by albumin, a blood protein it lets go of easily. ³ The 1 to 2% that is free, plus the loosely albumin-bound part, makes up bioavailable testosterone, the portion that can enter cells and do the work. Free testosterone is that unbound sliver on its own.

SHBG is the reason total testosterone can mislead. When SHBG rises, it holds more testosterone in the bound pool, so the total goes up even if the free, usable amount has not changed. When SHBG falls, the total drops for the same reason. SHBG rises with older age, hyperthyroidism, liver disease, and estrogen; it falls with obesity, insulin resistance, type 2 diabetes, and hypothyroidism. ¹³

In practice, most people start with total testosterone. You reach for free testosterone when the total sits near the lower limit or when SHBG is likely distorted, which is exactly when the total is least trustworthy. The reference method for free testosterone is equilibrium dialysis (a lab technique that physically separates the free hormone); many quick 'direct free T' immunoassays are unreliable, so a calculated free testosterone from total plus SHBG is often used instead. ³

What does low testosterone mean?

Low testosterone (which doctors call hypogonadism) as a diagnosis has two halves, and both have to agree. One half is symptoms; the other is two low morning tests. A single low reading is unreliable on its own: testosterone varies enough day to day that roughly one in three low readings returns to normal on a repeat. ¹ The low testosterone diagnosis needs the blood and the symptoms pointing the same way.

We recommend making a diagnosis of hypogonadism only in men with symptoms or signs consistent with testosterone deficiency and unequivocally and consistently low serum testosterone concentrations.Endocrine Society Clinical Practice Guideline (Bhasin et al., JCEM 2018)

The symptoms that track the number best are the sexual ones. The European Male Ageing Study found that reduced morning erections, low libido, and erectile dysfunction, combined with a total testosterone below about 317 ng/dL (11 nmol/L) and a low free testosterone, identified late-onset low testosterone; the non-sexual complaints like fatigue and low mood tracked the number poorly. ⁴

If a low is confirmed, the next fork is why. LH and FSH, two pituitary signals, split the causes: high LH and FSH point to the testes (primary), while low or normal LH and FSH point to the pituitary or hypothalamus (secondary). That split, and the reversible causes like acute illness, obesity, opioids, and steroids, belong to the low testosterone workup.

Who should test, and how often

Testing makes sense when there is a reason to test. The Endocrine Society advises against screening the general male population who have no symptoms. ¹ Consider a morning total testosterone if you have:

• Sexual symptoms: low libido, erectile dysfunction, or fewer morning erections
• Physical signs: loss of muscle or strength, new breast tissue, or a low-trauma fracture or osteoporosis
• Conditions linked to low testosterone: type 2 diabetes, obesity, known pituitary or testicular disease, HIV with weight loss, or infertility
• Medications that lower it: long-term opioids or glucocorticoids

There is no fixed retesting schedule for a normal, symptom-free result. The one firm rule is to confirm any low value with a second morning, fasting draw before acting on it. If symptoms are clear but the first number is normal, a repeat and a free testosterone are reasonable next steps to discuss with your clinician.

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